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References

J. Manassen, Platinum Metals Rev. 1971, 15

4), 142N. Kohler and F. Dawans, Rev. Znst. Fr.Petrole 1972, 27 105

K . G. Allurn, R D. Hancock, S. McKenzieand R. C. Pitkethly, Proc 5th Znternat. Cong.Catalysis Palm Beach, 1972

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G. W. Parshal1,J. Am. Chem. SOC. 972, 94,8716

G. J. K. Acres, G. C. Bond, B. J. Cooper andJ. A Dawson,J. Catalysis r966, 6 139

P. R. Rony, J. Catalysis 1969, 14 42

K . K Robinson, F. E. Paulik, A Hershmanand J. F. Roth,J. Catalysis 1969,15,245

W. 0 Haag and D. D. Whitehurst, BelgianPatent 721,686, 1969

R. L. Lazcano and J. E. Germain, Bull. SOC.Chim. Fr. 1971, 1869

B.P. CO.Ltd., U.S. Patent 3,726,809, 1973

Z . M. Michalska and D. E. Webster, un-published observations

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M. Capka, P. Svoboda, M. Cerny and J.Hetflejs, Tetrahedron Lett. ~9 71 , 787

B.P. Co. Ltd., British Patent 1,277,737, I972

For example see reference 16

18 H. Niebergall,Makromol. Chenz. 1962,52,218

19 B.P. Co. Ltd., British Patent 1,291,237, 1972

20 B.P. CO.Ltd., British Patent 1,295,673, I972

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22 B.P. Co. Ltd., British Patent 1,287,566, I972

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24 J P. Collman, L. S. Hegedus, M . P. Cooke,J. R. Norton, G. Dolcetti and D. N.Marquardt,J . Am. Chem. SOC.,972, 94 1789

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27 H. S. Bruner and J. C. Bailar, J . Am . Chem.

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Weld Metal Temperature Measurement

HARPOON TECHNIQUE WITH RHODIUM PLATINUM THERMOCOUPLES

The thermal history of weld metal gives a

good indication of the behaviour of the weld

thereafter. For example, the thermal be-

haviour of the weld bead affects the pro-

perties of transformable steel. T o record the

thermal history of a weld bead platinum

metal thermocouples may be inserted during

the welding process but until recently many

of them melted in use and the instruments

became open circuit.

C. Pedder of the Welding Institute’s

Metallurgical Department at Abington Hall,

Cambridge, has now described a simpletechnique in which platinum: 1 3 per cent

rhodium-platinum harpoon thermocouples

of 0 5 mm wire arc used. The wires are

insulated in twin bore ceramic insulators

supported in a close-fitting steel tube so that

they protrude 3 mm beyond the insulator,

which itself protrudes 5 mm beyond the steel

tube end. They dip into the pool of weld

metal which completes the circuit by acting

as the thermocouple hot junction. Tes ts

showed similar results to those using con-

Platinum Metals Rev. 1974, 18 2)

ventional thermocouples up to IOOO~C.The e.m.f.s differed by less than 0.01mV

10°C t IOOO’C).

Manual and semi-automatic methods have

been used to plunge the thermocouple

accurately into the weld metal pool. In the

latter case the welder can also operate the

harpoon thermocouple, and when used with

implant cracking test equipment the thermo-

couple records the thermal cycle and also

actuates the implant loading mechanism at the

predetermined temperature.

Weld thermal cycles and cooling times havebeen measured by the harpoon thermocouple

for the MMA, MIG and submerged arc

processes. It has also made possible the

thermal analysis of weld metal austenite

transformation immediately after deposition,

whereas previous dilatometry studies gave

transformation characteristics of reheated

metal. The thermal analysis process uses a

differential amplifier to convert thermocouple

output t o a voltage proportional to the cooling

rate. F J. S.

73